Tag Cloud Widget adds a simple tag cloud widget that you can use anywhere on your blog. This plugin looks at all your tags and displays them in a widget. The more times a tag is used, the larger the tag is.

Each tag is a link to the tag page (e.g. http://your-site.com/tag/your-tag). This will help with SEO.

Currently, there aren't any options to customize the tag cloud. It should work well out of the box. In the future, there may be options to customize the widget.

Will this help with SEO?

Yes, Google's bots can now run Javascript. This means that it will be able to crawl the links in the tag cloud. This will increase the number of inbound links on your blog and improve your SEO.